1. Field of the Invention
The present invention relates to an image forming apparatus configured such that a drum unit is attachable to and detachable from a body along a drum shaft.
2. Related Art
In an image forming apparatus such as a copy machine or a printer, an image supporting unit, which has a surface uniformly charged by a charging device, is optically scanned by an optical scanning device, and an electrostatic latent image corresponding to image information is formed on the surface of the image supporting unit such as a photoreceptor drum. Thereafter, the electrostatic latent image is developed by a developing device using toner as a developer, and visualized as a toner image. The toner image is transferred onto a sheet of paper by a transfer device, and then heated, pressurized and fixed onto the sheet of paper by a fixing device. The sheet of paper onto which the toner image is fixed is discharged outside the image forming apparatus, so that a series of image forming steps is terminated.
Incidentally, an image forming apparatus is known in which a photoreceptor drum, a charging device and the like are unitized into a drum unit for easy maintenance and the drum unit is configured to be attachable to and detachable from a body. In such an image forming apparatus employing the features described above, a drum shaft for driving the drum unit is provided in the body such that the drum unit is attached to the body by inserting the drum shaft into an axial center (hollow portion) of the photoreceptor drum and pushing the drum unit along a guide rail and the drum shaft, which are provided in the body. When the attachment of the drum unit is completed, the drum unit is positioned at a regular position by a positioning part provided in the body.
As a setup of positioning an optical deflection unit with respect to a frame of the body, it is known that a V-shaped notch is provided in a bottom surface on an end side of the optical deflection unit and a flange is provided on another end of the optical deflection unit. This setup causes the V-shaped notch formed in the optical deflection unit to engage with a reference shaft of the drum unit, such that the flange of the optical deflection unit is positioned above a height adjustment screw.
Another setup is also known, in which a process cartridge (a drum unit) is inserted into a cartridge slot of the body. In such a setup, a guide portion formed on the process cartridge is inserted along a pair of guide rails. Such a setup includes a technical feature that allows one of the guide rails to be movable in order to implement better handling associated with attachment and detachment of the process cartridge with respect to the body of the image forming apparatus. In the setup described above, the process cartridge is supported by an abutting member of the body when the one of guide rails is lowered through operation of a lever of the body. Accordingly, the positioning part of the process cartridge engages with a groove of the body, so that the process cartridge is positioned with respect to the body.